1, A running neo4j server on localhost:7474, preferably with the UUID plugin installed (optional).
Change application.yml to your password (or set in n the command line).
2, A constraint:

    create constraint on (n:`User`) assert n.`email` is unique

mvn spring-boot:run

curl http://192.168.1.79:8080/create-user

curl -X POST http://localhost:8080/oauth/token -u client:password -d grant_type=password -d [email protected] -d password=1234 -i

Both request fails on the master branch. Switch to the workaround branch, and both works as expected.